JP2019000882A - Arc welding method and solid wire - Google Patents

Abstract

To provide an arc welding method that has excellent feeding properties and high arc stability during arc welding, and a solid wire.SOLUTION: In a gas shield arc welding, Ar-containing gas, and a solid wire 10 having a steel core wire 11 and a copper plating film 12 formed on the surface of the steel core wire 11, with the copper plating film 12 having an average crystal grain size of 600 nm or less, are used to perform welding. Preferably the copper plating film 12 has an average crystal grain size of 50 nm or more and 500 nm or less.SELECTED DRAWING: Figure 1

Description

  The present embodiment relates to an arc welding method and a solid wire.

  Solid wire is widely used for gas shielded arc welding for thin plates of automobiles and the like. When welding using solid wire, wire feedability is excellent in short-term welding. However, if welding is performed for a long period of time, the tip wears out due to fusion with the solid wire and the arc becomes unstable. Cheap.

  Here, when a copper plating film is formed on the surface of the solid wire, it is generally known that tip wear is reduced and the arc is stabilized during welding. For example, Patent Document 1 discloses a solid wire having a copper plating film of 0.3 to 1.1 μm formed on the surface.

JP 2008-194716 A Japanese Patent No. 6044369

  By the way, in gas shielded arc welding using a solid wire, a welding method (wire feed control short-circuit arc welding method) is known in which the solid wire is repeatedly fed and controlled in the forward and backward directions (see, for example, Patent Document 2). In this welding method, the wire is advanced while arcing, the molten metal at the tip of the molten wire is brought into contact with the molten pool to extinguish the arc, then the wire is pulled back to move the molten metal, and the arc is emitted again. Sputtering is reduced by repeating the advancement of the wire.

  However, when feeding control is performed in the forward / backward direction of the solid wire in this way, the surfaces of the solid wire and the inside of the torch or liner slide inside the torch or inside the conduit cable (liner) to form a solid wire. The copper plating film may be worn out. In this case, the chip fusion cannot be sufficiently reduced during welding, causing problems such as deterioration in feeding resistance and unstable arc.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an arc welding method and a solid wire that have excellent feedability and high arc stability during arc welding.

  As a result of intensive studies on the arc welding method using a solid wire with a copper plating film formed on the surface, the present inventors have suppressed the wear of the copper plating film by reducing the crystal grain size of the copper plating film. I found out that I can do it. Furthermore, it has been found that the slidability of the solid wire can be improved, and, for example, in arc welding in which feed control is performed in the forward and backward direction of the solid wire, the feedability can be improved and the arc during welding can be made more stable. It was. The present invention has been made based on this finding.

  That is, the arc welding method of the present invention includes a gas containing Ar, a steel core wire, and a copper plating film formed on the surface of the steel core wire, and the average crystal grain size of the copper plating film is 600 nm or less. Welding is performed using a solid wire.

One aspect of the arc welding method of the present invention is characterized in that the solid wire is welded while being repeatedly fed and controlled in the forward / backward direction of the solid wire.
Here, the advancing / retreating direction means the forward direction and the reverse direction of wire feeding.

  One aspect of the arc welding method of the present invention is characterized in that the steel core wire is made of mild steel.

  In one aspect of the arc welding method of the present invention, the solid wire is, in mass%, C: 0.02% to 0.15%, Si: 0.2% to 2.0%, Mn: 0.00. It contains 2% or more and 3.0% or less, and Cu: 0.05% or more and 0.5% or less.

  Further, according to one aspect of the arc welding method of the present invention, the solid wire is further mass%, S: 0.30% or less, Al: 0.1% or more and 1.0% or less, Mo: 0.1 %: 3.0% or less, Ti: 0.01% or more and 0.3% or less, and Zr: 0.01% or more and 0.3% or less.

  One aspect of the arc welding method of the present invention is characterized in that the average crystal grain size of the copper plating film is 50 nm or more and 500 nm or less.

  The solid wire of the present invention is a solid wire comprising a steel core wire and a copper plating film formed on the surface of the steel core wire, and the average crystal grain size of the copper plating film is 600 nm or less It is characterized by.

  One aspect of the solid wire of the present invention is characterized in that the steel core wire is made of mild steel.

  One aspect of the solid wire of the present invention is, in mass%, C: 0.02% to 0.15%, Si: 0.2% to 2.0%, Mn: 0.2% to 3.0% % Or less, and Cu: 0.05% or more and 0.5% or less.

  One aspect of the solid wire of the present invention is further, in mass%, S: 0.30% or less, Al: 0.1% or more and 1.0% or less, Mo: 0.1% or more and 3.0% or less, It is characterized by containing at least one of Ti: 0.01% or more and 0.3% or less and Zr: 0.01% or more and 0.3% or less.

  One aspect of the solid wire of the present invention is characterized in that the average crystal grain size of the copper plating film is 50 nm or more and 500 nm or less.

  ADVANTAGE OF THE INVENTION According to this invention, the arc welding method and solid wire which are excellent in feeding property at the time of arc welding and have high arc stability can be provided.

FIG. 1 is a cross-sectional view of a solid wire according to an embodiment of the present invention. FIG. 2 is an example of a measurement result of a solid wire section by EBSD.

  Hereinafter, an arc welding method and a solid wire according to an embodiment of the present invention will be described with reference to the drawings.

The arc welding method according to the embodiment of the present invention is a gas shielded arc welding method using the solid wire 10 shown in FIG. First, the solid wire 10 will be described. The solid wire 10 includes a steel core wire 11 and a copper plating film 12 formed on the surface of the steel core wire 11. In the present specification, the solid wire may be simply referred to as a wire.
The steel core wire 11 is a wire made of steel having a circular cross section. In the present embodiment, the steel core wire 11 is mild steel, but is not limited thereto.

  The copper plating film 12 is formed on the surface of the steel core wire 11 using a plating solution such as copper sulfate or copper pyrophosphate. In the present embodiment, the copper plating film 12 having an average thickness of 2 μm or less, for example, is formed by performing wire drawing after copper plating is performed on the steel core wire.

  In this embodiment, the average crystal grain size of the copper plating film is 600 nm or less. When the average crystal grain size of the copper plating film is 600 nm or less, wear of the copper plating film can be satisfactorily suppressed. From the viewpoint of better suppressing the wear of the copper plating film, the average crystal grain size of the copper plating film is preferably 500 nm or less. More preferably, it is 450 nm or less. Note that the average crystal grain size of the copper plating film is practically 50 nm or more.

The average crystal grain size of the copper plating film in the present embodiment is the area ratio of each crystal grain when a copper plating film having a cross section perpendicular to the longitudinal direction of the wire is measured using an EBSD (Electron Back-Scattered Diffraction) apparatus. This is a diameter that takes into account. For example, the diameter d ′ considering the area ratio is the ratio of one crystal grain to the total area (c1, c2, c3,...) And each crystal grain diameter (d1, d2, d3,... Is a numerical value calculated from
d '= c1d1 + c2d2 + c3d3 + ...
It is represented by Here, the ratio of one crystal grain to the total area (c1, c2, c3,...) Is the number of points (n1, n2, n3,...) And the total number of each crystal grain. It is a numerical value calculated from the number of measurement points n,
c1 = n1 / n
It is. Therefore,
d '= (n1 / n) d1 + (n2 / n) d2 + (n3 / n) d3 +
As a result, the diameter d ′ in consideration of the area ratio is calculated. In the present embodiment, this d ′ is referred to as an average crystal grain size.

  FIG. 2 is an example in which EBSD measurement is performed on the copper plating film 12 in a cross section orthogonal to the longitudinal direction of the solid wire 10 according to the embodiment of the present invention. More specifically, FIG. 2 is an IPF map, in which an orientation difference between crystal grains is 15 ° or more as a grain boundary. In this example, there are no coarse crystal grains having a grain size of 1 μm or more. The average crystal grain size d ′ of the copper plating film 12 shown in FIG. 2 is about 460 nm. In FIG. 2, the lower side is a steel core wire (base material) 11.

  Further, the copper plating film 12 is formed by refining crystal grains by performing wire drawing processing and dynamic recrystallization after plating formation. The grain size of the copper plating film after plating is a mixed grain structure in which crystal grains of 1 μm or more and crystal grains with smaller grain sizes are mixed. As the size is reduced, the crystal grain size becomes more uniform. In the present embodiment, in the copper plating film 12 after dynamic recrystallization by wire drawing, crystal grains having a grain size exceeding 1 μm are not observed.

The solid wire 10 is a wire having a circular cross section with a diameter of 0.6 mm to 1.8 mm, for example. The composition of the solid wire 10 is not particularly limited, but C: 0.02% by mass to 0.15% by mass, Si: 0.2% by mass to 2.0% by mass, Mn: 0.00%. It is preferable that 2 mass% or more and 3.0 mass% or less, Cu: 0.05 mass% or more and 0.3 mass% or less are included. Below, the reason for limitation of each component is demonstrated.
In addition, content of these each element is content with respect to the wire total mass. Moreover, in this specification, the percentage (mass%) based on mass is synonymous with the percentage (weight%) based on weight.

(C: 0.02% by mass or more and 0.15% by mass or less)
C in the welding wire or the weld metal affects the spatter generated during welding. As for sputtering, there is no particular lower limit because there is no problem even if the content is small, but it is practical that it is 0.02% by mass or more. On the other hand, if oxygen is contained in a large amount, it is combined with oxygen during welding and becomes CO gas, generating bubbles on the surface of the droplets. For this reason, it is preferable to prescribe | regulate content of C as 0.15 mass% or less. More preferably, it is 0.12 mass% or less, More preferably, it is 0.10 mass% or less. C also affects the strength of the weld metal, and is preferably 0.04% by mass or more in order to ensure the strength.

(Si: 0.2% by mass or more and 2.0% by mass or less)
Si in the welding wire is a deoxidizing element and is an element that has an effect of ensuring the strength and toughness of the weld metal. If the addition amount is small, blowholes may be generated due to insufficient deoxidation, so it is preferable to contain 0.2% by mass or more. More preferably, it is 0.4 mass% or more. On the other hand, if Si is contained in a large amount, a large amount of slag is generated during welding, which may reduce the welding workability. For this reason, the Si content is preferably 2.0% by mass or less. More preferably, it is 1.5 mass% or less, More preferably, it is 1.0 mass% or less. In addition, when reducing generation | occurrence | production of slag, it is preferable to make content of Si 0.7 mass% or less.

(Mn: 0.2 mass% or more and 3.0 mass% or less)
Mn in the welding wire, like Si, is necessary for exerting an effect as a deoxidizer or sulfur scavenger and ensuring the strength and toughness of the weld metal. In order to suppress the occurrence of blowholes due to insufficient deoxidation, it is preferable to contain 0.2% by mass or more. More preferably, it is 0.4 mass% or more, More preferably, it is 0.5 mass% or more. On the other hand, if Mn is contained in a large amount, a large amount of slag may be generated during welding, or the strength may increase excessively and the toughness of the weld metal may be significantly reduced. For this reason, it is preferable that content of Mn is 3.0 mass% or less. More preferably, it is 2.0 mass% or less, More preferably, it is 1.3 mass% or less. In addition, when reducing generation | occurrence | production of slag, it is preferable to make content of Mn into 1.0 mass% or less.

(Cu: 0.05 mass% or more and 0.5 mass% or less)
Cu is mainly derived from the copper plating film and contained in the wire, but also includes Cu contained in the steel core wire. When the amount of Cu is too small, the substrate may be exposed. Therefore, Cu is preferably 0.05% by mass or more. On the other hand, when there is too much Cu, the plating film is easily peeled off, so Cu is preferably 0.5% by mass or less.

  In some embodiments, the balance of the solid wire is Fe and inevitable impurities. If necessary, at least one selected from S, P, Al, Mo, Ti, and Zr may be further added within the following range. Other unavoidable impurities include, for example, N, O, Cr, Ni, and the like. In a solid wire, it is practical that N or O is 90 ppm or less. Cr, Ni, etc. may be positively added.

(S, P: 0.30 mass% or less)
S (sulfur) and P (phosphorus) are both impurity elements, and it is preferable to make the content as small as possible. For this reason, a lower limit is not set, but it is practical that each is 0.001% by mass or more. . If these are present in large amounts exceeding 0.30% by mass, weld metal cracks may occur. Therefore, it is preferable to regulate both to 0.30 mass% or less (including 0%).

(Al: 0.1% by mass or more and 1.0% by mass or less)
Al is an element that contributes to slag aggregation. Although the addition of Al is not essential, if the Al content is less than 0.1% by mass, it is difficult to obtain a coagulation effect of slag. Therefore, when adding Al, the content is 0.1% by mass or more. It is preferable to make it 0.2% by mass or more. On the other hand, if the Al content exceeds 1.0% by mass, spattering may occur frequently. Therefore, when adding Al, the content is preferably 1.0% by mass or less, more preferably 0.7% by mass or less, and particularly preferably 0.4% by mass or less. preferable.

(Mo: 0.1 mass% or more and 3.0 mass% or less)
Mo is an element that contributes to improvement in strength. Although addition of Mo is not essential, in order to exhibit such an effect well, when adding Mo, the content is preferably 0.1% by mass or more, and 0.3% by mass or more. It is more preferable. On the other hand, when Mo exceeds 3.0% by mass, the effect is saturated because it forms an intermetallic compound with Fe at a high temperature. Therefore, when adding Mo, the content is preferably 3.0% by mass or less, more preferably 2.0% by mass or less, and even more preferably 1.5% by mass or less. .

(Ti: 0.01% by mass or more and 0.3% by mass or less)
Ti is a strong deoxidizing element and has the effect of improving the strength and toughness of the weld metal. When Ti is contained, it is preferable to contain 0.01% by mass or more. If it is contained in a large amount exceeding 0.3% by mass, a large amount of slag is generated during welding, and welding workability may be lowered. For this reason, it is preferable to regulate the Ti content in a range of 0.3 mass% or less.

(Zr: 0.01 mass% or more and 0.3 mass% or less)
Zr has the effect of improving arc stability. When Zr is contained, it is preferable to contain 0.01% by mass or more. However, when the Zr content is large, the scale layer after the annealing process becomes thick and the adhesion of the scale may increase. Therefore, the upper limit of the Zr content is preferably 0.3% by mass.

(Production method)
Although the manufacturing method of the solid wire 10 which concerns on embodiment of this invention is demonstrated below, it is not limited to this. First, molten steel having a predetermined component composition is melted using a converter, an electric furnace, or the like, and a steel material (a billet or the like) is produced from the obtained molten steel by continuous casting, an ingot forming method, or the like. Next, after the manufactured steel material is heated, it is hot-worked and further subjected to dry cold rolling (cold drawing) to obtain a steel strand having a diameter of about 3 to 8 mm, for example. Next, the steel wire is annealed or pickled as necessary, and is subjected to copper plating and wire drawing to produce a solid wire 10 having a final wire diameter (for example, 0.6 to 1.8 mm). In addition, in this embodiment, a well-known thing can be used as a plating bath at the time of copper plating.

  Here, in this embodiment, it is necessary to perform a wire drawing process for controlling the average crystal grain size of the copper plating film. Generally, a solid wire is drawn after copper plating. In the wire drawing after copper plating, dynamic recrystallization and crystal grain growth occur in the copper plating film. That is, dynamic recrystallization occurs due to the introduction of strain due to processing, and the crystal grains become finer, and crystal grains grow due to heat generation due to processing, and the crystal grains become coarse. For example, Japanese Patent Application Laid-Open No. 2012-143796 describes that the wire surface is exposed to a high temperature of 400 ° C. or higher during wire drawing. As described above, when the copper plating film is exposed to a high temperature during processing heat generation, the average crystal grain size grows to over 600 nm.

  Therefore, in this embodiment, in the copper plating film, the growth of crystal grains is suppressed while dynamic recrystallization occurs. The frequency of occurrence of dynamic recrystallization can be controlled, for example, by adjusting the strain rate. Specifically, the wire drawing rate for one pass is 20% or less, more preferably 15% or less, and even more preferably 10% or less. For wire drawing of a solid wire, there is a method using a hole die or a roller die. However, when a hole die is used, the strain rate is likely to be larger than that of a roller die, so that it is preferable to reduce the wire drawing rate. In order to suppress the growth of crystal grains, it is preferable to cool the roll or to inject oil in order to reduce the temperature of the copper plating film during processing. The wire may be cooled in advance to a temperature lower than room temperature. As described above, the copper plating film 12 according to the embodiment of the present invention is obtained.

  Next, an arc welding method according to an embodiment of the present invention will be described. The arc welding method according to the embodiment of the present invention is performed using the solid wire 10 described above and a gas containing Ar.

The shield gas used in the welding method according to the embodiment of the present invention only needs to contain Ar, and may consist only of Ar. Alternatively, in addition to Ar, CO ₂ , O _2, or the like may be contained. For example, about 5 to 30% by volume of CO ₂ to O ₂ and the balance of Ar may be used. The shield gas can also contain N ₂ , H _2, etc. as inevitable impurities. In the arc welding method according to the embodiment of the present invention, known welding conditions can be appropriately employed as the welding conditions. In addition, the material to be welded that is to be welded is not particularly limited, and can be applied to various steel plates.

  According to the solid wire 10 and the arc welding method according to the present embodiment configured as described above, the average crystal grain size of the copper plating film 12 is 600 nm or less. In the liner or torch, the copper plating film is not easily damaged, the feedability is improved, and the arc can be stabilized. In other words, when the copper plating film is energized inside the torch, it is energized while the copper plating film is well formed, so that chip fusion is stable, feedability is improved, and arc generation is also stable. To do. In particular, even when feeding control is repeatedly performed in the forward and backward directions of the wire, the surface of the copper plating film is less likely to cause sliding wear and scraping with the contact object, and feedability and arc stability are improved. Here, the advancing / retreating direction means the forward direction and the reverse direction of wire feeding.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples, and may be implemented with modifications within a range that can be adapted to the gist of the present invention. All of which are within the scope of the present invention.

Various solid wires having a diameter of 1.2 mm having the composition shown in Table 1 and the average crystal grain size of the copper plating film are manufactured by the method described in the embodiment and the like. Welding was performed under the following conditions while feeding control (wire feeding control short-circuit arc welding method).
(1) Steel plate A steel plate having a length of 200 mm, a width of 60 mm, and a thickness of 3.2 mm was used. The steel type of the steel plate is SPHC590.
(2) Welding posture Horizontal fillet welding was performed.
(3) Shielding gas Ar + 20 volume% CO ₂ was used as the shielding gas.
(4) Welding current and welding voltage Welding was carried out at a welding current of 240 A, a welding voltage of 18 V, and a welding speed of 100 cm / min.

  In addition, the wire from which the average crystal grain diameter of a copper plating film differs was produced by changing the conditions of wire drawing variously. In the conventional examples 1 to 3, the dynamic recrystallization and crystal grain growth are not controlled at the time of manufacture, and the crystal grain size of the copper plating film is over 600 nm. Comparative Example 1 is an example using a wire that was heat-treated at 200 ° C. for 10 minutes in an inert gas atmosphere with respect to the wire used in Invention Example 24.

  The average crystal grain size was obtained using data measured in a cross section orthogonal to the longitudinal direction of the wire using an EBSD device (TSL OIM crystal orientation analyzer). The average crystal grain size is a diameter d ′ in consideration of the area ratio, and can be easily calculated by software attached to the apparatus. In addition, the numerical value of the average crystal grain size was rounded off to a multiple of 10 and rounded. The analysis range of EBSD was 12.5 μm × 12.5 μm, and the measurement was performed under the condition of step 0.035 μm.

  About wire feeding, it carried out on the conditions which have two bending parts between 6 m using a commercially available wire feeder. As for the wire feedability, ◎ indicates that the occurrence of copper plating powder is particularly low in the supply path, ◎ indicates that the generation of copper plating powder is particularly good, ○ indicates that the generation of copper plating powder is low, ○ indicates copper plating powder Those with a large number of occurrences were marked as x as unsatisfactory. The good wire feedability means that the copper plating film is less likely to be worn or scraped when the wire is fed.

  Regarding the arc stability of the welding wire, the arc during the welding operation is visually evaluated, and it is particularly good if the arc is consistently stable. ○ was given as the case, and X was given as the case where the arc was not consistently stable.

  In Table 1, the wire component (% by mass) represents the amount of each component (% by mass) per the total mass of the wire. The balance is Fe and inevitable impurities. Note that “−” means that the element is included as an inevitable impurity.

  As shown in Table 1, Examples 1 to 26 of the present invention in which the average crystal grain size of the copper plating film of the wire was 600 nm or less were particularly good or good in feeding property and arc stability.

  On the other hand, Conventional Examples 1 to 3, in which the average crystal grain size of the copper plating film of the wire is over 600 nm, were not good in feedability and arc stability. Similarly, Comparative Example 1 in which the average crystal grain size of the copper-plated film of the wire is over 600 nm also has poor feedability and arc stability.

10 Solid wire 11 Steel core wire 12 Copper plating film

Claims (11)

A gas containing Ar;
A solid wire having a steel core wire and a copper plating film formed on the surface of the steel core wire, the average crystal grain size of the copper plating film being 600 nm or less;
An arc welding method characterized in that welding is performed using   The arc welding method according to claim 1, wherein the solid wire is welded while being repeatedly fed and controlled in the advancing and retreating direction of the solid wire.   The arc welding method according to claim 1, wherein the steel core wire is made of mild steel. The solid wire is
% By mass
C: 0.02% to 0.15%,
Si: 0.2% or more and 2.0% or less,
The arc welding method according to any one of claims 1 to 3, further comprising: Mn: 0.2% to 3.0% and Cu: 0.05% to 0.5%. .   The solid wire is further mass%, S: 0.30% or less, Al: 0.1% or more and 1.0% or less, Mo: 0.1% or more and 3.0% or less, Ti: 0.01 5. The arc welding method according to claim 4, comprising at least one of% to 0.3% and Zr: 0.01% to 0.3%.   The arc welding method according to any one of claims 1 to 5, wherein the average crystal grain size of the copper plating film is 50 nm or more and 500 nm or less. A solid wire comprising a steel core wire and a copper plating film formed on the surface of the steel core wire,
An average crystal grain size of the copper plating film is 600 nm or less.   The solid wire according to claim 7, wherein the steel core wire is made of mild steel. % By mass
C: 0.02% to 0.15%,
Si: 0.2% or more and 2.0% or less,
The solid wire according to claim 7 or 8, comprising Mn: 0.2% to 3.0%, and Cu: 0.05% to 0.5%.   Furthermore, in mass%, S: 0.30% or less, Al: 0.1% or more and 1.0% or less, Mo: 0.1% or more and 3.0% or less, Ti: 0.01% or more and 0.3% 10. The solid wire according to claim 9, comprising at least one of:% or less and Zr: 0.01% or more and 0.3% or less.   The solid wire according to any one of claims 7 to 10, wherein the average crystal grain size of the copper plating film is 50 nm or more and 500 nm or less.